1. Technical Field
This invention relates to remote sensing in general, and particularly to systems for determining the ocean's surface velocity based on changes in sea surface temperature from satellite-based thermal imagers.
2. Background Technology
Imaging of the world's oceans from space provides large-area synoptic views, and sequential images of the same scene allow us to calculate sea surface velocities. These two-dimensional velocity fields can be very useful in understanding the dynamics of the ocean. Researchers have employed a number of schemes to calculate sea surface velocities from Sea Surface Temperature (SST), but perhaps the two that have received the most widespread use are the Maximum Cross Correlation (MCC) technique of Emery et al. “An Objective Method for Computing Advective Surface Velocities from Sequential Infrared Satellite Images”, J. Geophys. Res., Vol. 91, pp. 12865-12878, 1986, and the heat equation INVerse model (INV) described in Kelly, K. A., (1989), “An Inverse Model for Near-Surface Velocity from Infrared Images”, J. Phys. Ocean., Vol. 19, pp. 1845-1864, 1989 and in Kelly, K. A., and P. T. Strub, “Comparison of Velocity Estimates from Advanced Very High-Resolution Radiometer in the Coastal Transition Zone, J. Geophys. Res., Vol. 97, pp. 9653-9668, (1992).
The INV model has also been used to infer the properties of the ocean surface mixed layer. For example, Ostrovskii and Piterbarg have inverted an advection-diffusion equation for the upper ocean mixed layer in different areas of the Pacific Ocean for velocity, as well as vertical mixed layer entrainment velocity and horizontal diffusivity, as described in A. Ostrovskii and L. Piterbarg, “Inversion for Heat Anomaly Transport from Sea-Surface Temperature Time-Series in the Northwest Pacific, J. Geophys. Res., Vol. 100, pp. 4845-4865, (1995) and in Ostrovskii AG, L. I. Piterbarg, “Inversion of Upper Ocean Time Series for Entrainment, Advection, and Diffusivity”, J. Phys. Ocean., Vol. 30, pp. 201-204, (2000).
In Vigan, X., C. Provost, R. Bleck, and P. Courtier, (2000), “Sea surface velocities from sea surface temperature image sequences 1. Method and validation using primitive equation model output”, J. Geophys. Res., 105, 19499-19514 and Vigan. X. et al., “Sea Surface Velocities from Sea Surface Temperature Image Sequences 2. Application to the Brazil-Malvinas Confluence Area”, J. Geophys. Res., 105, 19515-19534. (2000), model-generated data is used to demonstrate the method in the Brazil-Malvinas confluence region. In Zavialov, P. O. et al., “An Inverse Model for Seasonal Circulation over the Southern Brazilian Shelf: Near-Surface Velocity from the Heat Budget,” J. Phys. Ocean., 28, 545-562, 1998, a similar calculation was performed for the same region using sea surface temperature mapped from in-situ measurements.